1. Field of the Invention
The invention relates to a method for producing a tableting additive, to the tableting additive thus obtained and to the use of the said additive. The additive is in particular a lactose additive.
2. Description of the Related Art
Usually spray dried materials, such as lactose, consist of crystalline and amorphous material. In the case of lactose, spray dried particles comprise monohydrate lactose and amorphous lactose. Unlike crystalline lactose, amorphous lactose is a hygroscopic material. It will readily take up moisture from the surrounding atmosphere. This moisture uptake reduces the glass transition temperature of amorphous lactose drastically: from 104° C. at 0% moisture content in the amorphous material down to 37° C. with 7.2% moisture content for example and even further down to 5° C. at ca. 14% moisture content. Hence, when the moisture content in the amorphous material has reached a critical value, the glass transition temperature Tg is lower than the ambient temperature, and the amorphous material changes from a glassy state into a rubbery state. Then molecular rearrangements occur and the amorphous material crystallises.
Thus, the amorphous form is not stable and may crystallise into the monohydrate form. When this crystallisation occurs in the presence of the active ingredient, such as a drug, it may become bound in the crystal. For tablets, the disintegration properties are important. When due to the hygroscopic character of the amorphous lactose in the tablets, crystallisation occurs over time, this may affect the disintegration properties and the bioavailability of the active ingredient thus altering the performance of the tablet.
It is therefore desirable to stabilise the tableting additive, such as lactose, in order to avoid changes in bioavailability and disintegration behaviour.